#define  _CRT_SECURE_NO_WARNINGS


#include <stdio.h>

int main()
{
	int a;
	float i = 1;
	float j = 2;
	float k = 0;
	float sum = 0;
	for (a = 1; a <= 20; k = j,j += i,i = k, a++)
	{
		sum += j / i;
	}
	printf("%f", sum);
	return 0;
}